Power Supply Subsystem for Powering a Node Over Communication Cabling

1. A power supply subsystem configured to provide electrical power to at least node over communication cabling, the power supply subsystem comprising: a management and control unit; a combiner combining power into the communication cabling substantially without interfering with data communication between a local area network (LAN) switch and the at least one node over the communication cabling; and a current limiting circuitry controlling current of said power combined into said communication cabling via said combiner, said current limiting circuitry comprising a comparator and arranged to: compare said current of said power combined into said communication cabling for each of said at least one node with a first threshold and a second threshold, said first threshold lower than said second threshold; and provide delayed current cut-off responsive to said first threshold being exceeded and immediate current limiting at said second threshold; wherein said management and control unit is operative to interrogate the at least one node to which it is intended to transmit power over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.

2. A power supply subsystem according to claim 1 , wherein said interrogation of the at least one node comprises measuring the voltage across the communication cabling connected to the at least one node and determining whether said measured voltage is within a predetermined range.

3. A power supply subsystem according to claim 2 , wherein in the event that said measured voltage is within said predetermined range, the at least one node is classified as a Power over LAN node.

4. A power supply subsystem according to claim 1 , wherein said interrogation of the at least node comprises measuring the voltage across the communication cabling connected to the at least node and determining whether said measured voltage exceeds a predetermined voltage threshold.

5. A power supply subsystem according to claim 1 , wherein said combiner comprises at least one coupler.

6. A power supply subsystem according to claim 4 , wherein in the event said measured voltage exceeds said predetermined voltage threshold, the at least one node is classified as a Power over LAN node.

7. A power supply subsystem according to claim 1 , wherein said management and control unit is further operative to output a report pertaining to the status of the at least one node.

8. A power supply subsystem according to claim 7 , wherein said report includes a report of at least one characteristic of the at least one node.

9. A power supply subsystem according to claim 8 , wherein said at least one characteristic comprises an indication of power consumption of the at least one node.

10. A power supply subsystem according to claim 1 , wherein said power is combined onto wire pairs of the communication cabling providing data communication between the at least one node and the LAN switch.

11. A power supply subsystem according to claim 1 , wherein said power is transmitted over wire pairs of said communication cabling providing data communication between the at least one node and the LAN switch.

12. A power supply subsystem according to claim 1 , further comprising a power supply, said combiner combining power from said power supply into the communication cabling.

13. A power supply subsystem according to claim 1 , wherein said management and control unit is further operative to determine the status of the associated communication cabling over which it is intended to transmit power.

14. A local power supply subsystem according to claim 13 , wherein said interrogation and said status determination is achieved by a plurality of measurements of at least one of voltage and current, said plurality of measurements being accomplished at a plurality of predetermined times.

15. A power supply subsystem configured for connection between a local area network (LAN) switch and at least one node, the power supply subsystem providing electrical power to the at least node over communication cabling, the power supply subsystem comprising: a management and control unit; at least one port for data connection to a LAN switch; at least one port for connection of communication cabling to the at least one node; a combiner combining power into the communication cabling substantially without interfering with data communication between the LAN switch and the at least one node; and current limiting circuitry controlling current of said power combined into said communication cabling via said combiner, said current limiting circuitry comprising a comparator and arranged to: compare said current of said power combined into said communication cabling for each of the at least one node with a first threshold and a second threshold, said first threshold lower than said second threshold; and provide delayed current cut-off responsive to said first threshold and immediate current limiting responsive to said second threshold, wherein said management and control unit is operative to interrogate the at least one node to which it is intended to transmit power over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.

16. A power supply subsystem configured for connection between a LAN switch and at least one node, the power supply subsystem providing electrical power to the at least node over communication cabling, the power supply subsystem comprising: a management and control unit; at least one port for connection to a LAN switch; a combiner combining power into the communication cabling substantially without interfering with data communication between the LAN switch via the at least one port and the at least one node; and current limiting circuitry controlling current of said power combined into said communication cabling via said combiner, said current limiting circuitry comprising a comparator and arranged to: compare said current of said power combined into said communication cabling for each of the at least one node with a first threshold and a second threshold, said first threshold lower than said second threshold; and provide delayed current cut-off responsive to said first threshold without limiting current in excess of said first threshold, and immediate current limiting at said second threshold, wherein said management and control unit is operative to interrogate the at least one node to which it is intended to transmit power over the communication cabling in order to determine whether the node's characteristics allow it to receive power over the communication cabling.

17. A power supply subsystem configured for connection between a LAN switch and at least one node, the power supply subsystem providing electrical power to the at least node over communication cabling, the power supply subsystem comprising: a management and control unit; at least one port for data connection to a LAN switch; a combiner combining power into the communication cabling substantially without interfering with data communication between the LAN switch and the at least one node; and current limiting circuitry controlling current of said power combined into said communication cabling via said combiner, said current limiting circuitry comprising a comparator and arranged to: compare said current of said power combined into said communication cabling for each of the at least one node with a first threshold and a second threshold, said first threshold lower than said second threshold; and provide delayed current cut-off responsive to said first threshold without limiting current in excess of said first threshold, and immediate current limiting responsive to said second threshold.

18. A power supply subsystem according to claim 1 , wherein said current limiting circuitry is further arranged to not limit current between said first threshold and said second threshold prior to said delayed current cut-off.

19. A power supply subsystem according to claim 1 , wherein said current limiting circuitry comprises a comparator and a switch, the output of said comparator being coupled to said switch to provide said immediate current limiting.

20. A power supply subsystem according to claim 15 , wherein said current limiting circuitry comprises a comparator and a switch, the output of said comparator being coupled to said switch to provide said immediate current limiting.

21. A power supply subsystem according to claim 16 , wherein said current limiting circuitry comprises a comparator and a switch, the output of said comparator being coupled to said switch to provide said immediate current limiting.

22. A power supply subsystem according to claim 17 , wherein said current limiting circuitry comprises a comparator and a switch, the output of said comparator being coupled to said switch to provide said immediate current limiting.